Influence of ceramic paste formulation and processing on extrudability

Szymiczek, Marcin (2025). Influence of ceramic paste formulation and processing on extrudability. University of Birmingham. Eng.D.

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Abstract

A study was undertaken of ceramic paste extrusion process with ram and single screw extruders (RE and SSE). The work focus was to deepen the understanding of correlations between paste characteristics in RE and SSE phenomena affecting extrudability. Research areas included peptisable and unpeptisable powders, liquid phase migration (LPM), flow visualisation and developing a methodology to interpret it. Previous studies of paste flow visualisation used simple (colouring, ex situ) and advanced (magnetic resonance, in situ) techniques to assess visual differences. This work extended the simple approach by calculating elongation time (quantification factor) from Mascia et al. (2006).

The ram extruder was geometrically scaled to reveal effects of using the same apparent shear rate and to devise a basis for quantification of visualised flow. Larger LPM in the smaller arrangement was ascribed to lower volumetric flow rate and contributed to an increased static zone. These observations were crucial in establishing measurements of flow features (two angles and mapping points of flow line).

Peptisable principal powder formulations (zeolite, soft spheres) had a higher die inflow pressure in RE than unpeptised ones (glass spheres, hard spheres). Colloidal interactions made the flow profile more elastic (stretched vertically, higher pressure), whereas the latter was dominated by hear (flatter, lower pressure).

A correlation was found between the elongation quantified inside the RE at 321.1 s^{-1} and SSE at 10 rpm (relative and paste velocities). This finding has the potential to predict volumetric flow rate in SSE that is not known a priori.

Type of Work:

Thesis (Doctorates > Eng.D.)

Award Type:

Doctorates > Eng.D.

Supervisor(s):